Effect of pH on the ultrastructure of the conidial wall of Aspergillus niger aggregate conidia and its relationship to zearalenone adsorption

2016 ◽  
Vol 9 (3) ◽  
pp. 389-395
Author(s):  
C.M. Pereyra ◽  
L.R. Cavaglieri ◽  
V. Poloni ◽  
S.M. Chiacchiera ◽  
A. Cristofolini ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Experimental Data ◽  
Aspergillus Niger ◽  
Surface Adsorption ◽  
Theoretical Models ◽  
Dense Layer ◽  
Effect Of Ph ◽  
Transmission Electron ◽  
Conidial Surface ◽  
Chemical Groups

The purpose of the present study was to evaluate the effect of pH on the ultrastructure of the conidial wall of dead conidia harvested from the non-toxicogenic Aspergillus niger aggregate strain RC084 and its relationship to zearalenone (ZEA) adsorption capacity. Moreover, mathematical models were applied to explain the interaction between conidia and ZEA absorbance. A ZEA adsorption test was performed using a concentration of 1×107 dead conidia/ml at pH 2 and 6 at 37 °C for 30 min. Unbound ZEA was quantified by high-pressure liquid chromatography. The ZEA adsorption was strongly dependent on the pH of the medium; the highest values were 2.2×10-6 μg ZEA/conidia at pH 6. Isotherms representing the amount of bound ZEA as a function of ZEA concentration in equilibrium after adsorption have typical S- or L-shapes. The experimental data could be fitted to the Frumkin-Fowler-Guggenheim (FFG) and Hill theoretical models. The ultrastructure of the conidial wall was studied by infrared spectroscopy (IR) and transmission electron microscopy (TEM). The representative IR spectra showed that pH did not produce significant changes in the different chemical groups. However, ultrastructure studies by TEM detected considerable changes in the organisation of the conidial wall. This is the first study showing that the loss of the outermost electron dense layer, responsible for the ornamentations on the conidial surface. Adsorption is favoured at pH 6".

scholarly journals A novel exosome biogenesis mechanism: multivesicular structures budding and rupturing at the plasma membrane

2019 ◽  
Author(s):  
Stephanie Leon Quinonez ◽  
Ian R. Brown ◽  
Helen E. Grimsley ◽  
Jindrich Cinatl ◽  
Martin Michaelis ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Plasma Membrane ◽  
Membrane Association ◽  
Dense Layer ◽  
Physiological Processes ◽  
Exosome Biogenesis ◽  
Transmission Electron ◽  
Typical Morphology ◽  
Intercellular Signalling ◽  
Microscopy Images

AbstractExosomes are small vesicles secreted by the cells, which mediate intercellular signalling and systemic physiological processes. Exosomes are known to originate from the intraluminal vesicles of the multivesicular endosome that fuses with the plasma membrane. We found that the non-small cell lung cancer (NSCLC) cell lines, HCC15 and A549, secreted exosomes with typical morphology and protein contents. Unexpectedly, transmission electron microscopy images indicated that the cells formed multivesicular structures that protruded from the plasma membrane and ruptured to release the exosomes. There were smooth multivesicular structures surrounded by an ordinary looking membrane, multivesicular structures coated by an electron dense layer with regular spacing pattern, and intermediate forms that combined elements of both. Electron microscopy images suggested that exosomes are release from these structures by burst events and not by the conventional fusion process. The molecular details of this novel mechanism for membrane association, deformation and fusion is to be unveiled in the future.

scholarly journals Determination of Displacement Fields at the Sub-Nanometric Scale

Materials ◽  
2019 ◽  
Vol 12 (11) ◽  
pp. 1804
Author(s):  
Cesar A. Sciammarella ◽  
Federico M. Sciammarella ◽  
Luciano Lamberti
Keyword(s):  
Electron Microscopy ◽  
Theoretical Models ◽  
The Other ◽  
Nanometer Scale ◽  
Displacement Fields ◽  
Eulerian Description ◽  
Transmission Electron ◽  
Displacement Information ◽  
Crystalline Array

Macroscopic behavior of materials depends on interactions of atoms and molecules at nanometer/sub-nanometer scale. Experimental mechanics (EM) can be used for assessing relationships between the macro world and the atomic realm. Theoretical models developed at nanometric and sub-nanometric scales may be verified using EM techniques with the final goal of deriving comprehensive but manageable models. Recently, the authors have carried out studies on EM determination of displacements and their derivatives at the macro and microscopic scales. Here, these techniques were applied to the analysis of high-resolution transmission electron microscopy patterns of a crystalline array containing dislocations. Utilizing atomic positions as carriers of information and comparing undeformed and deformed configurations of observed area, displacements and their derivatives, as well as stresses, have been obtained in the Eulerian description of deformed crystal. Two approaches are introduced. The first establishes an analogy between the basic crystalline structure and a 120° strain gage rosette. The other relies on the fact that, if displacement information along three directions is available, it is possible to reconstruct the displacement field; all necessary equations are provided in the paper. Remarkably, the validity of the Cauchy-Born conjecture is proven to be correct within the range of observed deformations.

Centromere structure and chromosome number in mitosis of the colourless phytoflagellate Polytoma papillatum (Chlorophyceae, Volvocales, Chlamydomonadaceae)

Genome ◽  
1995 ◽  
Vol 38 (6) ◽  
pp. 1249-1254 ◽  
Author(s):  
Klaus Werner Wolf
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Chromosome Number ◽  
Higher Plants ◽  
Attachment Site ◽  
Dense Layer ◽  
Mitotic Metaphase ◽  
Serial Sections ◽  
Transmission Electron ◽  
Alternative Approach

Centromere structure is described in mitosis of the unicellular biflagellate alga Polytoma papillatum using transmission electron microscopy. The kinetochores are five-layered elements at the poleward surface of the chromosomes. The five layers consist of three dense plates interspersed by two transparent zones. The polemost dense layer serves as the attachment site for kinetochore microtubules and the innermost dense layer is intimately associated with the chromatin. The five-layered organization of the kinetochore in the alga is unusual. In animals, three-layered kinetochores are the rule. This type has also been found in some algae, while higher plants do not possess striated kinetochores. An attempt was made to determine the chromosome number of P. papillatum. Individual chromosomes could not be recognized with confidence, since there were numerous lateral contacts between the chromosomes throughout mitosis. An alternative approach, however, was successful. Counting the kinetochores in serial sections through mitotic metaphase and anaphase plates revealed a number of 15 chromosomes.Key words: anaphase, kinetochore, metaphase, microtubule.

Phase diagrams and thermodynamics of rare-earth-doped zirconia ceramics

2007 ◽  
Vol 79 (10) ◽  
pp. 1731-1753 ◽  
Author(s):  
Chong Wang ◽  
Matvei Zinkevich ◽  
Fritz Aldinger
Keyword(s):  
Electron Microscopy ◽  
Experimental Data ◽  
Phase Diagrams ◽  
Heat Content ◽  
X Ray Diffraction ◽  
Zirconia Ceramics ◽  
X Ray ◽  
Transmission Electron ◽  
Diagram Approach ◽  
Rare Earth Doped

Results of the comprehensive experimental and computational phase studies of the systems ZrO2-REO1.5 (RE = La, Nd, Sm, Gd, Dy, Yb) are summarized. Various experimental techniques, X-ray diffraction (XRD), scanning electron microscopy (SEM), electron probe microanalysis (EPMA), transmission electron microscopy (TEM), differential thermal analysis (DTA), and high-temperature calorimetry are employed to study the phase transformation, phase equilibria between 1400 and 1700 °C, heat content and heat capacity of the materials. A lot of contradictions in the literature are resolved, and the phase diagrams are reconstructed. Based on the experimental data obtained in this work and literature, the systems ZrO2-REO1.5 are thermodynamically optimized using the CALPHAD (CALculation of PHase Diagram) approach. Most of the experimental data are well reproduced. Based on the present experiments and calculations, some clear characteristic evolutions with the change of the ionic radius of doping element RE+3 can be concluded.

scholarly journals Exploiting the Acceleration Voltage Dependence of EMCD

Materials ◽  
2021 ◽  
Vol 14 (5) ◽  
pp. 1314
Author(s):  
Stefan Löffler ◽  
Michael Stöger-Pollach ◽  
Andreas Steiger-Thirsfeld ◽  
Walid Hetaba ◽  
Peter Schattschneider
Keyword(s):  
Electron Microscopy ◽  
Experimental Data ◽  
Transmission Electron Microscopy ◽  
Elastic Scattering ◽  
Voltage Dependence ◽  
Atomic Scale ◽  
Electron Wave ◽  
Magnetic Signal ◽  
Transmission Electron ◽  
Acceleration Voltage

Energy-loss magnetic chiral dichroism (EMCD) is a versatile method for measuring magnetism down to the atomic scale in transmission electron microscopy (TEM). As the magnetic signal is encoded in the phase of the electron wave, any process distorting this characteristic phase is detrimental for EMCD. For example, elastic scattering gives rise to a complex thickness dependence of the signal. Since the details of elastic scattering depend on the electron’s energy, EMCD strongly depends on the acceleration voltage. Here, we quantitatively investigate this dependence in detail, using a combination of theory, numerical simulations, and experimental data. Our formulas enable scientists to optimize the acceleration voltage when performing EMCD experiments.

About the Influence of Silver Nanoparticles on Living Organisms Physiology

2016 ◽  
Vol 14 (4) ◽  
pp. 42-51 ◽  
Author(s):  
Orkhan А Zeinalov ◽  
Svetlana P Kombarova ◽  
Dmitry V Bagrov ◽  
Mariya A Petrosyan ◽  
Gulrukhsor H Tolibova ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Experimental Data ◽  
Silver Nanoparticles ◽  
Biochemical Analysis ◽  
Nanosized Particles ◽  
Laboratory Mice ◽  
Pathological Conditions ◽  
Transmission Electron ◽  
Biocidal Products ◽  
Living Organisms

The production and properties of silver-containing products currently attract increasing attention due to the unique properties of silver. Specific properties of silver are considerably amplified when it is dispersed to the form of nanosized particles. Silver nanoparticles are several times more active than its other forms and many antibiotic and biocidal products. At the same time nanoparticles can more easily penetrate the protective barriers of living organisms and get directly into their tissues and organs. To be assured of safety of silver nanoproducts for human health and environment, it is necessary to study the influence of silver nanoparticles on the physiology of living organisms. This paper presents experimental data on effect of two nanosilver preparations (poviargol and argovit) on laboratory mice. Investigated preparations were characterized by transmission electron microscopy. It was established that morphological express control of peripheral blood and biochemical analysis of blood serum of living organisms can serve for purposes of primary monitoring of the pathological conditions caused by silver nanoparticles.

The Role of Carbon Contamination in Suspended Gold Nanowires

2002 ◽  
Vol 738 ◽  
Author(s):  
Sergio B. Legoas ◽  
Douglas S. Galvão ◽  
Varlei Rodrigues ◽  
Daniel Ugarte
Keyword(s):  
Electron Microscopy ◽  
Experimental Data ◽  
Density Functional ◽  
Gold Nanowires ◽  
Interatomic Distances ◽  
Carbon Contamination ◽  
Linear Chains ◽  
Transmission Electron ◽  
New Phenomena

ABSTRACTMetallic nanowires represent very interesting systems due to new phenomena such as quantum conductance and unexpected long interatomic distances attaining 0.3–0.5 nm. These large distances represent a challenge for physical interpretation. In this work we present experimental data from transmission electron microscopy and results from ab initio density functional calculations for suspended gold chains. We show that large distances as 0.5 nm can be easily explained by the presence of carbon atoms as contaminants, while distances ranging from 0.29 up to 0.36 nm might be explained as resulting of a mixture of clean stressed and contaminated linear chains.

scholarly journals Impact of copper and its nanoparticles on growth, ultrastructure, and laccase production of Aspergillus niger using corn cobs wastes

BioResources ◽  
2020 ◽  
Vol 15 (2) ◽  
pp. 3289-3306
Author(s):  
Tarek M. Abdel Ghany ◽  
Marwah M. Bakri ◽  
Aisha M. H. Al-Rajhi ◽  
Mohamed A. Al Abboud ◽  
M. M. Alawlaqi ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Aspergillus Niger ◽  
Copper Nanoparticles ◽  
Laccase Production ◽  
Acidic Ph ◽  
Corn Cobs ◽  
Transmission Electron ◽  
Incubation Periods ◽  
Fungus Growth

The influence of copper and its nanoparticles was studied relative to growth and ultrastructure of Aspergillus niger. Laccase production by A. niger using corn cobs as substrate at different concentrations of CuSO4 and copper nanoparticles (CuNPs) is reported. Fungus growth was induced at 100 ppm of CuNPs and CuSO4, while at 300 ppm, the growth inhibition was 65.6% and 86.9%, respectively. Fungus sporulation was reduced to 30.4% and 47.6% at 300 ppm of CuNPs and CuSO4, respectively, compared to the control (100%). Transmission electron microscopy revealed that CuSO4 and CuNPs treatments encouraged the deformed appearance of the fungus at 200 ppm and 300 ppm, particularly CuNPs. The CuNPs and CuSO4 induced laccase production at 1.67 U/mL and 1.51 U/mL at optimum concentrations 0.15 mM and 0.25 mM, respectively. The optimum concentrations of CuNPs and CuSO4 led to reduced incubation periods of 12 d and 14 d, respectively, required to produce the highest amount of laccase (1.66 U/mL and 1.53 U/mL), while without treatments, the incubation period increased to 16 d required for the highest amount of laccase production (1.36 U/mL). Induction of laccase production at acidic pH and at 30 °C was recorded with the addition of CuSO4 and CuNPs, while its effects were slight at pH above 6.

scholarly journals DEVELOPMENT OF NEW SYNTHESIS ROUTES FOR HYDROXYAPATITE NANOPOWDERS PRODUCTION FROM CHICKEN EGGSHELLS

Química Nova ◽  
2021 ◽  
Author(s):  
Ingrid Lima ◽  
Bonifácio Fialho ◽  
Renata Simão ◽  
Daniele Nogueira ◽  
Fernanda Sampaio ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Rietveld Method ◽  
Calcium Phosphates ◽  
Good Surface ◽  
Transmission Electron ◽  
New Synthesis ◽  
Electron Microscopy Analysis ◽  
Synthesis Routes ◽  
Co Precipitation ◽  
Chemical Groups

Hydroxyapatite (HA) nanopowders are attracting interest for surface application to ceramic biomaterials. In this study, we developed innovative and new viable synthesis routes of calcium phosphate nanopowders from the natural calcium carbonate of chicken eggshells. Following the four routes, alternative co-precipitation, vacuum process, brushite, and calcination, we obtained the HA samples, which were then characterized by different methods. The X-ray diffraction /Rietveld method showed the HA phases, monetite and brushite crystallinity with greater symmetry, and nanoscale. Transmission electron microscopy showed the morphology of nanoparticles functionalized nanoparticles smaller than 100 nm in routes A, B and D, and Fourier-transform infrared spectrophotometry and Raman spectroscopy identified the classic chemical groups of calcium phosphates by four routes mainly groups (PO4) 3- and (CO3 -). Scanning electron microscopy analysis revealed a good surface topography to future cell biointeraction in A, B and D routes, and thermogravimetric analysis showed the mass loss profile inherent to each synthesis route with slot at 200 °C. Hence, the eggshell HA and brushite and the specific monetite nanoparticles with different morphology can be prepared from the four new possible and viable routes using different methods.

Effects of Cymbopogon nardus (L.) W. Watson essential oil on the growth and morphogenesis of Aspergillus niger

2001 ◽  
Vol 47 (1) ◽  
pp. 9-17 ◽  
Author(s):  
Virginia G de Billerbeck ◽  
Christine G Roques ◽  
Jean-Marie Bessière ◽  
Jean-Louis Fonvieille ◽  
Robert Dargent
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Aspergillus Niger ◽  
Essential Oil ◽  
Normal Growth ◽  
Inhibitory Effect ◽  
Mycelium Growth ◽  
Cymbopogon Nardus ◽  
Transmission Electron ◽  
Hyphal Diameter

The growth inhibitory effect of Cymbopogon nardus (L.) W. Watson var. nardus essential oil on Aspergillus niger (Van Tieghem) mycelium was determined on agar medium. The mycelium growth was completely inhibited at 800 mg/L. This concentration was found to be lethal under the test conditions. Essential oil at 400 mg/L caused growth inhibition of 80% after 4 days of incubation, and a delay in conidiation of 4 days compared with the control. Microscopic observations were carried out to determine the ultrastructural modifications of A. niger hyphae after treatment with C. nardus essential oil. The main change observed by transmission electron microscopy concerned the hyphal diameter and the hyphal wall, which appeared markedly thinner. These modifications in cytological structure might be caused by the interference of the essential oil with the enzymes responsible for wall synthesis which disturb normal growth. Moreover, the essential oil caused plasma membrane disruption and mitochondrial structure disorganization. The findings thus indicate the possibility of exploiting Cymbopogon nardus essential oil as an effective inhibitor of biodegrading and storage-contaminating fungi.Key words: essential oil, antifungal agent, hyphal ultrastructure, cell wall, scanning electron microscopy, transmission electron microscopy.

Sign in / Sign up

Export Citation Format

Share Document